In the manufacture of nuclear fuel rods, one end of a hollow tube cladding is closed with an end plug and nuclear fuel pellets are inserted into the open end. A sealing plug, or end plug as sometimes referred to in the industry, having an axial bore therethrough, is positioned adjacent the open end and girth welded to the hollow tube. The axial bore communicates with the passage of the tube. During girth welding, air and fumes are drawn from the tube through the axial bore. The tube then is pressurized with a nonoxidizing gas by passing the gas through the sealing plug axial bore. The sealing plug then is seal welded to close the axial bore.
These two welds, the seal and girth weld, typically have been performed at separate girth and seal welding stations. For example, U.S. Pat. No. 4,188,521 to Yeo, discloses a single station girth welding apparatus for girth welding a sealing plug to a nuclear fuel rod. After girth welding, subsequent seal welding of the axial bore is performed. However, for economy of space, increased weld quality, and reduced welding and tube transport time, girth and seal welding now have been performed in the same pressurization chamber. For example, in commonly assigned and allowed patent application Ser. No. 07/373,076 filed Jun. 29, 1989 by Robert Duncan, now U.S. Pat. No. 4,971,750, an end stop is adapted for engaging a sealing plug positioned in a fuel rod. The fuel rod is inserted into a girth and seal welding chamber. A welding electrode extends through an axial passage of the end stop for facilitating the seal welding closure of the sealing plug bore. An air channel extends between the axial passage and an outlet on the surface of the end stop and includes a one-way ball valve for permitting the free passage of gas from the tube, and through the end stop axial passage while precluding passage of gas in the reverse direction.
In this type of apparatus, the seal welding electrode tip can be damaged during multiple girth welding operations. During girth welding the tip of the welding electrode is disposed adjacent the axial bore of the sealing plug. Hot gases are drawn through the axial opening and engage the tip of the seal welding electrode fixed within the axial opening. These hot gases typically erode the electrode. As a result, production down time increases and production costs increase because the end stop and seal welding electrode must be changed. Also, the heat generated during seal welding can damage the end stop unless the end stop is moved out of engagement with the sealing plug during the seal welding operation.